Hi, everyone.

We plan to purchase a linux cluster with AMD dual opteron dual core processors.

Does anyone know how many parallel CFX licenses you need for dual core processors? 1 license for a dual core processor or 2 licenses for a dual core processors?

Thanks.

1 parallel license per processor. a dual core counts as two processors.

Woodcrest CPU might be faster

More precise: 1 cfx license for your job and additional 1 parallel license per core.

In my experience you get better performance when you turn the dual core processing off rather than running a parallel job across the two cores. You need to do a benchmark to see.

James

Thanks for your replies.

Since a dual core processor is not as efficient as 2 single core processors, running a job on a dual core using two parallel licenses seems like a waste.

How do you turn the dual core processing off? Can I easily have it turn on and off?

On my Intel machine, you just turn it off in the bios. I'm not sure if you can do that on all machines.

With AMD chips, running on two cores of the same CPU is just as efficient as running on two different CPUs. So, there's no need to try to turn off one of the cores. Mike

Hi,

Also with the latest release of Intel chips (Woodcrest) they also have very little loss in running two cores simultaneously.

Glenn Horrocks

Performance and efficiency are not the only issues when assessing platforms. Power/Cooling and Footprint are especially important when using large clusters. Dual cores use less power than the equivalent two-processor single cores. This results in a lower power system for roughly the same performance and a smaller footprint (i.e. half the racks) for roughly the same performance. Lower power systems need less cooling and hence the cooling system uses less power. This is VERY important when running clusters (~>100 procs ~80-100kw) where the infrastructure is limited in terms of power, cooling and space. The cost of running these machines in terms of electrical power should also be taken into account. Performance is not the be all and end all of CFD platforms! Buying the latest and greatest biggest baddest machines money can buy will only result in grief when it fries!

Hi Bob,

You are correct for large clusters but as the vast majority of CFX customers run it either serial or on small clusters (I would guess up to 8 nodes) then things like power consumption and size are of little importance.

Glenn Horrocks

Wrong Patrick.

If I run a case on 4 processors, the following licenses are used:

1 acfx_solver 1 acfx_parallel 4 acfx_par_proc

I think it is totally unreasonable to pay additional licenses to enable CFX to run on dual core processors. What will happen when quad and eigth's processors are becomming the standard CPU? It's like having to pay 3 times more when CPU speed increased from 1 GHz to 3 GHz.